Memory chips are used for persistent storage of data in order to store not only program data, such as firmware or an operating system, for example, but also configuration data or user data on a device. The device may be a field device or a controller, for example. In practice, this frequently involves the use of separate memory modules, for example for storing the firmware and the configuration data.
Such memory modules may be permanently installed in a device or interchangeable. An example of a permanently installed memory module is a soldered serial EEPROM. Interchangeable memory modules are what is known as a C plug, an ID plug, an SD card (secure digital memory card) or a USB stick, for example. These memory modules are frequently partially or completely overwritten during the period of use of a device, for example in order to change configuration data of a field device. In order to protect security-relevant data, in particular security-relevant configuration data, on the field device, for example, memory modules are frequently used that permit access to the memory modules only if the user has authenticated himself beforehand. These security-protected memory chips particularly have the advantage that production thereof is much more complex and more expensive and that use is awkward.